The growing availability of TV broadcast and interactive services creates a need for a new type of a TV control system that would facilitate user access to options offered by TV program providers. For example, direct broadcast satellite services require users to make their selection among about a thousand TV channels with various TV programs and services. Direct television satellite broadcasting is provided via direct broadcast satellites at an uplink frequency of 17.3 to 17.9 GHz and a downlink frequency of 12.2 to 12.7 Ghz.
A digital satellite television system for direct television broadcasting includes a transmitter for transmitting television signals including video and audio components to a satellite. The satellite retransmits the received television signals to an outdoor antenna assembly that includes a dish-like antenna and a block converter. The dish-like antenna directs the received television signals to the block converter that converts the frequencies of the received television signals to respective lower frequencies.
The television signals produced by the block converter are connected via a coaxial cable to an indoor satellite receiver coupled to a TV set. The satellite receiver tunes, demodulates and otherwise processes the received television signals to provide video and audio signals with a NTSC, PAL or SECAM format suitable for processing by the TV set that produces an image on a display screen in response to the video signals, and an audible response by means of speakers in response to the audio signals.
Within the transmitter, analog video and audio signals are converted to respective digital signals compressed according to the Motion Picture Expert Group (MPEG) encoding standard. The resultant digital signals are represented by a stream of packets including error correction data. The type of packets is identified by a header code. Packets corresponding to control data may also be added to the packet stream.
In the MPEG standard, the video information may be transmitted in the form of a luminance (Y) component and two color difference (U and V) components. For example, the first color difference component may represent the difference between the red image information and the luminance image information (R-Y), and the second color difference component may represent the difference between the blue image information and the luminance image information (B-Y). In addition, the color information is compressed because the two color difference components correspond to more than one picture element. The use of color difference components and the sharing of the color difference components between picture elements reduces the transmission bandwidth.
The digital information resulting from the compression and error correction encoding is modulated on a carrier using Quaternary Phase Shift Keying (QPSK) modulation and transmitted to a satellite for retransmission.
The satellite receiver comprises a tuner for selecting the appropriate carrier signal retransmitted by the satellite and for converting the frequency of the selected carrier to an intermediate frequency (IF) signal. A QPSK demodulator demodulates the IF signal and supplies it to an error-correcting decoder to correct demodulated packets representing video and audio information. An MPEG decoder decodes and decompresses video and audio packets to form digital video and audio signals supplied to a TV set. A TV set-top box serves to deliver compressed digital video and audio signals in real time usable form to one or more TV sets.
As the digital satellite television system may provide about 1,000 TV channels with various TV programs and services, a TV graphical user interface (GUI) may be displayed on the screen of a TV set to show a list of TV channels, programs and services. A conventional TV GUI uses a single layer of on-screen display graphics to present TV information. Multiple menus are provided on the screen to enable users to navigate through various types of presented information. Each time a new type of information is required, users should initiate a new menu of options to make a required selection among its options. To support this procedure, the host CPU wipes out the old menu and draws the new one. This reduces the speed of information update on the screen.
Further, such a multi-menu presentation requires a hierarchical menu system with multiple levels of graphical presentation. A hierarchical menu may be provided to allow users to make a selection among various menus. This often causes confusion as the users lose track of what menu they came from and how to get back. Also, it may be difficult to understand on which level of the hierarchical system the GUI currently operates.
Therefore, it would be desirable to provide a TV GUI that produces multiple layers of graphics on a TV screen to eliminate the need for a multi-menu hierarchical system.
Also, to produce various visual effects, it would be desirable to adjust graphical presentation in a higher layer of graphics to expose a predetermined portion of a lower layer of graphics.